All of the film transport equations are now formulated with respect to the film
volume fraction in the region cell layer rather than the film thickness which
ensures mass conservation of the film even as it flows over curved surfaces and
around corners. (In the previous formulation the conservation error could be as
large as 15% for a film flowing around a corner.)
The film Courant number is now formulated in terms of the film cell volumetric
flux which avoids the stabilised division by the film thickness and provides a
more reliable estimate for time-step evaluation. As a consequence the film
solution is substantially more robust even though the time-step is now
significantly higher. For film flow dominated problem the simulations now runs
10-30x faster.
The inconsistent extended PISO controls have been replaced by the standard
PIMPLE control system used in all other flow solvers, providing consistent
input, a flexible structure and easier maintenance.
The momentum corrector has been re-formulated to be consistent with the momentum
predictor so the optional PIMPLE outer-corrector loop converges which it did not
previously.
nonuniformTransformCyclic patches and corresponding fields are no longer needed
and have been removed which paves the way for a future rationalisation of the
handling of cyclic transformations in OpenFOAM to improve robustness, usability
and maintainability.
Film sources have been simplified to avoid the need for fictitious boundary
conditions, in particular mappedFixedPushedInternalValueFvPatchField which has
been removed.
Film variables previously appended with an "f" for "film" rather than "face"
have been renamed without the unnecessary and confusing "f" as they are
localised to the film region and hence already directly associated with it.
All film tutorials have been updated to test and demonstrate the developments
and improvements listed above.
Henry G. Weller
CFD Direct Ltd.
The writeEntry form is now defined and used consistently throughout OpenFOAM
making it easier to use and extend, particularly to support binary IO of complex
dictionary entries.
A new constraint patch has been added which permits AMI coupling in
cyclic geometries. The coupling is repeated with different multiples of
the cyclic transformation in order to achieve a full correspondence.
This allows, for example, a cylindrical AMI interface to be used in a
sector of a rotational geometry.
The patch is used in a similar manner to cyclicAMI, except that it has
an additional entry, "transformPatch". This entry must name a coupled
patch. The transformation used to repeat the AMI coupling is taken from
this patch. For example, in system/blockMeshDict:
boundary
(
cyclic1
{
type cyclic;
neighbourPatch cyclic2;
faces ( ... );
}
cyclic2
{
type cyclic;
neighbourPatch cyclic1;
faces ( ... );
}
cyclicRepeatAMI1
{
type cyclicRepeatAMI;
neighbourPatch cyclicRepeatAM2;
transformPatch cyclic1;
faces ( ... );
}
cyclicRepeatAMI2
{
type cyclicRepeatAMI;
neighbourPatch cyclicRepeatAMI1;
transformPatch cyclic1;
faces ( ... );
}
// other patches ...
);
In this example, the transformation between cyclic1 and cyclic2 is used
to define the repetition used by the two cyclicRepeatAMI patches.
Whether cyclic1 or cyclic2 is listed as the transform patch is not
important.
A tutorial, incompressible/pimpleFoam/RAS/impeller, has been added to
demonstrate the functionality. This contains two repeating AMI pairs;
one cylindrical and one planar.
A significant amount of maintenance has been carried out on the AMI and
ACMI patches as part of this work. The AMI methods now return
dimensionless weights by default, which prevents ambiguity over the
units of the weight field during construction. Large amounts of
duplicate code have also been removed by deriving ACMI classes from
their AMI equivalents. The reporting and writing of AMI weights has also
been unified.
This work was supported by Dr Victoria Suponitsky, at General Fusion
